Medium: sodium lauryl sulfate solution (2 in 100); 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C15H16O2 dissolved from the difference between UV absorbances at the wavelengths of maximum and minimum absorbance at about 270 nm and 296 nm, respectively, on filtered portions of the solution under test, suitably diluted with Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Nabumetone RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C15H16O2 is dissolved in 45 minutes.

Mobile phase— Prepare a solution of 6 mL of glacial acetic acid in 350 mL of water. Adjust with 1 N sodium hydroxide to a pH of 3.7, and dilute with water to obtain 400 mL. Prepare a filtered and degassed mixture of acetonitrile and this solution (3:2). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Nabumetone RS in a mixture of methanol and water (9:1) to obtain a solution having a known concentration of about 0.5 mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 500 mg of nabumetone, to a 1000-mL volumetric flask, add about 100 mL of water, and stir with the aid of a magnetic stirrer for 5 minutes. Dilute with methanol to volume, stir for another 15 minutes, and filter.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 280-nm detector and an 8-mm × 10-cm column that contains 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 1500 theoretical plates; the tailing factor is not more than 1.5; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of nabumetone (C15H16O2) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Nabumetone RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.